Generally, people on the autism spectrum tend to be personally cautious and socially withdrawn. As you would expect, previous research shows that people with autism tend to have low rates of substance abuse – the preference for low risk and avoidance of social situations means less drinking or drug use. But new research from the Washington University School of Medicine found the opposite: in their study of 3,080 Australian twins, people with symptoms of autism were more likely than people without symptoms to abuse alcohol and marijuana. The interesting reason why and perhaps implications for protecting both autistic people and those who happen to be socially withdrawn are inside their fascinating research.

First, people on the autism spectrum are a tricky group to study – because the spectrum includes many people with mild symptoms like those of Asperger’s syndrome, the less extreme side of the spectrum which may go undiagnosed. And so instead of studying people formally diagnosed with autism, in this case the researchers asked people about their symptoms that tend to be related to autism. How would alcohol and marijuana use correlate with symptoms like social-interaction difficulties, communication challenges and a tendency to engage in repetitive behaviors?

Interestingly, what they found is that people with autistic traits were no more likely to drink or use marijuana than people without these traits, but that people with autistic traits who drank or smoked pot were more likely to become addicted to or otherwise abuse these substances

In their study, just under 20 percent of twins without autistic traits met the criteria for alcoholism. But of people with autistic traits, 35 percent were alcohol-dependent. With marijuana, 23 percent of the controls had used marijuana more than 10 times in their lives, compared with 39 percent of people with six or more autistic symptoms.

In a press release accompanying the research, Duneesha De Alwis, PhD, a postdoctoral fellow in the Department of Psychiatry, wrote, “People with autistic traits can be socially withdrawn, so drinking with peers is less likely. But if they do start drinking, even alone, they tend to repeat that behavior, which puts them at increased risk for alcohol dependence.”

But what about previous findings that people with autism are protected from substance abuse? The answer, according to the researchers, is the difference between symptoms and diagnosis. Think about it: a diagnosis is likely to accompany a more extreme form of the disorder. And it seems from this research as if a more extreme form of the disorder may keep autistic people from even experimenting with substances.

But then at the level of individual symptoms or even clusters of symptoms, “It could be that some traits related to autism are protective, while others elevate the risk for alcohol and substance-abuse problems,” says Arpana Agrawal, PhD, associate professor of psychiatry at the university.

If autism itself is protective, autistic tendencies may be a risk factor for substance abuse. Which autistic symptoms increase the risk? Are people with only one or two autistic tendencies at higher risk or are there tipping points on the spectrum that increase and then decrease risk? Agarwal, De Alwis and colleagues are asking these questions in further research. For the time being, I would love to hear your experience with autism, symptoms that could be considered autistic, and substance abuse. What’s your take on the intersection of these challenges?

Richard Taite is founder and CEO of Cliffside Malibu, offering evidence-based, individualized addiction treatment based on the Stages of Change model. He is also co-author of the book Ending Addiction for Good.

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